If you want to buy something (which means you first need a permanent visa) in Tokyo, count about 3000 euros (so about 2000 pounds) per square metre. Of course it could be 2000 or 5000 depending on the proximity to the station, city center, age of the building, etc.
If you want to rent, you can already find something for 40.000-50.000 yen/month (200-250 pounds) in Tokyo. I guess it's a bit cheaper in Nagano, but not sure.